The applications of Internet of Things have emerged in every aspect of people’s life. The volume of data gathered can be enormous. Enterprises and personal consumers are increasingly reliant on cloud storage services instead of local storage. While they enjoy the convenience of cloud storage services, they also worry about the integrity of the cloud-stored data since they do not physically own the data. To enable public integrity auditing, third-party auditors as trusted ones verify data integrity on behalf of the data owner. However, the vulnerability of auditors should also be considered. We propose a consortium blockchain-based public integrity verification system (CBPIV). In CBPIV, the auditor behaviors are recorded in the consortium blockchain so that authorized parties can audit the auditor to see if the verification results are correct. A smart contract is deployed to check the behavior of the auditor automatically, which can trigger alerts for unusual behaviors. The evaluation on both security and performance shows that our proposed scheme is secure and alleviates the burden on data owners of limited computation capability.

Cloud storage services offer flexible, convenient solutions for business and personal users to store data. Traditionally, Third Party Auditors (TPAs) are introduced to ensure data integrity for public auditing. However, TPAs may also be untrusted for forging the auditing results or colluding with cloud storage servers to deceive users. In this paper, we propose a novel Blockchain-based Public Auditing Outsourcing system without TPAs (BPAO), in which the computationally expensive operations in public auditing are outsourced through blockchain to the cloud servers without risking users' privacy. Our security analysis indicates that BPAO achieves soundness and robustness. The experimental results show that BPAO is computationally efficient for cloud storage user.

In the practical applications of supervised learning methods, the high cost of obtaining labeled data for learning tasks is a critical problem. One promising research area for solving the problem is transfer learning, which aims to learn a task in target domain by utilizing the training data in a different but related source domain. In this article, we propose a novel heterogeneous transfer learning algorithm called Heterogeneous Daily Living Activity Learning (HDLAL) which derives domain invariant feature representation space from cross-domain data distributions by projecting both domain data into the derived space in the close proximity of each other using Maximum Mean Discrepancy. Within the new feature space, we utilize ensemble classification algorithm to train multi-label classifier using the projected data to predict the labels in the target domain. We show the effectiveness of our approach by experimenting on real-world smart home datasets. The results shows that our HDLAL algorithm outperforms the common direct learning approaches in the context of predicting labels of activities of daily living (ADL).

Software-Defined Networking (SDN) is an innovational network architecture which gives network administrators the ability to directly control the whole network by programming on a centralized controller. Due to network complexity, networks are unlikely to be bug-free. The ability to verify data plane properties will make network management easier for network administrators in SDN. In this paper, we present a novel atomic predicates based data plane properties verification method for SDN using Spark which is a big data processing framework. First, we verify packet reachability which is a fundamental data plane property. Then, we verify other data plane properties such as loop-freedom and nonexistence of black holes. In addition, the proposed method can detect a security threat existing in SDN called firewall bypass threat with packet reachability verification. By adopting atomic predicates, we achieve less computational and storage overhead. We implement the methods and study the performance. The results of experiments show that we can efficiently and accurately detect loops, black holes and firewall bypass threats.

TLS (Transport Layer Security) is a well-known protocol that provides authentication and private communication for application protocols like HTTP (Hypertext Transfer Protocol). In TLS, data transferred from the upper layer can be compressed before it is encrypted. When an E-mail attached file is transferred over TLS, its compression ratio may be degraded since there are certain restrictions on the transfer of the E-mail, such as the need for text encoding of binary data and the recompression of already compressed data. The authors have already proposed an improved compression method for TLS, however, if compression is combined with encryption, the information concerned may become readable, since the length of the encrypted (and compressed) data might allow eavesdroppers to guess what kind of data are being transferred. In order to solve this problem, this paper proposes a compression method, MAILComp, designed for electric mail transfer protocols such as SMTP (Simple Mail Transfer Protocol), POP (Post Office Protocol), and IMAP (Internet Message Access Protocol) over TLS. From network experiments, compression ratios and file transfer times for four kinds of E-mail were observed, with simulated bandwidth restrictions to represent four typical communication media. The results show that MAILComp will provide an effective secure compression method whose overhead is virtually identical to that of the original compression method for TLS.

Mobile IP is the current standard for supporting global mobility, however the performance degrades to support micro mobility. Cellular IP could be a good solution to accommodate efficiently hundreds of, thousands of mobile hosts that perform fast and frequent handoff in a small local area network. In semisoft handoff of cellular IP, a mobile host sends a semisoft packet to the new base station before performing actual handoff to guarantee that the routing cache mapping associated with the new base station is created before actual handoff takes place. But packet loss and handoff delay are still occurred by this model. We propose an advanced semisoft handoff method with no packet loss but with additional small packet delay just before or after handoff. In this method, the cross-over node calculates the time for the last message to be delivered to the mobile host via the old base station just before handoff based on four typical network models. On receiving that packet, the mobile host performs handoff to the new base station. Our simulation experiment results show that the proposed semisoft handoff method actually outperforms the traditional semisoft handoff method in both handoff packet loss and handoff delay. We study the performance of the advanced semisoft handoff method with the network models.

In order to protect a server to become overloading due to concentration of accesses, a mirror server system is widely used for distributing the load to multiservers. For such a system, it is very important for users to select an appropriate one among the servers. In the previous systems, the DNS (domain name system) Round-Robin mechanism is widely adopted for this purpose, otherwise users must choose a server by themselves. Even in the former method, however, since all servers are evenly assigned to clients without any cares of the performance and process status of the servers, the load of each server is deflected. To solve the above problem, this article proposes a new adaptive load balancing method based on the ordinary DNS Round-Robin mechanism. In this proposal, a DNS server for the mirror-server system periodically probes the status of each server. For a query from each client, the DNS server changes its response from the probed results and IP address of the client. Finally, the prototype system of the proposal is implemented and the file transfer speeds of both the proposed method and Round-Robin DNS method are estimated for the mirror server system of RingServer Project in Japan.

We propose a queue management method for improving TCP performance over a wireless link. With our proposed control method, packet loss in the wireless link is completely eliminated and all packets are delivered in the correct order. No change is required to TCP itself or to the servers. Our proposed method is implemented between the media access control (MAC) layer and logical link layer in a base station, and is designed to help the local retransmission control in the MAC layer. Computer simulation experiments show that our proposed method can maximize the bandwidth use of the wireless link at high bit error rate conditions under conventional TCP controls. The fairness problem of TCP communication between connections with different bit error rate in wireless link is also improved.

DiffServ (differentiated services) is proposed to define the priority level in an IP header. For the priority controls, CBQ (class based queueing) is also presented. In CBQ, a router prepares a queue for each class of the priority level, and assigns available bandwidth to the class. However, the upper limit of the available bandwidth for each class is fixed in CBQ, and any class usually, cannot obtain extra bandwidth beyond the upper limit. A lower priority class can borrow a part of bandwidth from a higher priority class, only when the average packet transfer rate in the higher priority class must be smaller than the expected rate defined by a certain threshold. Thus, if the higher priority class constantly has data to be transferred, the lower priority class cannot borrow any bandwidth, even if the higher priority class has enough queue space. From this problem, we introduced the dynamic bandwidth decision mechanism to CBQ. In the mechanism, the upper limit of the available bandwidth for each class is dynamically modified due to the size of the queue space in each class. The proposal method provides more flexible bandwidth control, and then increases the effectiveness of the whole network from the simulation experiments. This paper presents implementation methods of the dynamic bandwidth decision method for network processors. Finally, the methods are evaluated on the real network environments.

In this paper we propose an adaptive handoff algorithm based on the "threshold-with-hysteresis". In general, such handoff algorithms are proposed to improve the handoff decision for a specific user Our algorithm aims to provide effective network utilization for all users. To realize the handoff decision based on the mobile nodes, the agent advertisements include information of the congestion status at the base station in the algorithm. For implementing the algorithm to Mobile IP, we also propose the system architecture with a QoS mechanism. The simulation experiment shows that our proposed algorithm improves the average handoff blocking rate than the previous method in spite of low overhead of our expansion.

The specification of SSL/TLS defines that data from the upper layer can be compressed in the record layer before they are encrypted. Since only the no-compression is provided for the compression algorithm in the specification, nobody can compress transmission data at the SSL/TLS protocols unless communication peers have a special agreement to use a compression algorithm. However, the compression mechanism should be useful for the users of narrower bandwidth communication lines such as ordinary analog telephone lines and N-ISDN. In order to solve this problem, the paper first introduces general-purpose compression algorithms into SSL/TLS, and shows that the average transfer times for several Japanese text files via HTTP are much improved, especially for narrow bandwidth communication lines. We also compare it with the compression mechanism on HTTP, and the resulting difference between the results of the SSL/TLS compression and HTTP compression is rather small. For improving the compression ratio, we next propose compression algorithms specialized for application protocols. As examples, we focus to HTTP and HTML, and construct the tree structures of the field names and field values. From the tree, the static dictionaries for the compression algorithms are defined. Finally, we implement the compression algorithms and show the compression ratios when several HTML files are transferred.

Since wireless channel is always band-limited with multi-path fading and highly burst errors, flexible error control is needed in wireless asynchronous transfer mode (WATM) networks. This paper proposes a hybrid automatic repeat request (ARQ) strategy using rate-compatible punctured convolutional (RCPC) codes, which has on-demand quality of services (QoS). In order to increase the throughput of WATM networks, the packet size for the retransmission of ARQ protocol varies according to the types of services, and the coding rate for the payload of the WATM cell is adjusted to match the varying channel. In case of cell loss rate (CLR) being constrained, such as 10/sup -6/, the throughput is analyzed and found to be better than the existing schemes.

Because the wireless asynchronous transfer mode (ATM) networks are often constrained with the limited link bandwidth and error-prone characteristics, forward error correction (FEC) is needed to improve their bit error rate performance. In this paper, a two-level punctured convolutional code (PCC) scheme is constructed to apply to a wireless ATM cell header and various payloads with the flexible unequal error protection (UEP). Since their perforation matrices can be programmable, the code rates of PCC are applicable to the different sensitivity of source-encoded symbols, even if only the same encoding and decoding hardware is used. Finally, the performance on Gaussian and fading channels is analyzed, which shows significant reductions in cell loss rate (CLR) and good balances for CLR and the payload bit error rate (BER).

LOTOS formal description technique (FDT) is applied to the formal description of distributed systems and the specification of OSI protocol layers. LOTOS is difficult to understand and to learn because it is based on a mathematical model. In this paper, for supporting the knowledge acquisition of learners studying basic LOTOS, we suggest a new algorithm that can verify an equivalence relation, find an error location, and correct an error when the error occurs at another process. Finally, we give an example of a prototype program for an educational support system for basic LOTOS.